void SysTick_Delay_Nms(uint16_t Nms)

{    

  SysTick->CTRL=0;//??systick

  SysTick->LOAD=(uint32_t)Nms*9000; //?????????,9000??????,???1ms??? 

  SysTick->CTRL=0x01;               //bit0=1 ?????bit1=0 ????????bit2=0 ?????? 9MHz

  while(!(SysTick->CTRL&(1<<16))); //??bit16 ?????? ,???bit16=1

  SysTick->CTRL=0X00000000;         //?????

  SysTick->VAL=0X00000000;           //???????    

}  